the second verb must be either an infinitive with 'to' such as 'to do', 'to make', 'to go' etc. or an -ing form such as 'doing', 'making', 'going'. In this episode of The Flatmates, the police ...

Present participle (verb-ing) clauses can be used without a subject pronoun and an auxiliary when the subject of the sentence does two things at the same time or when one action interrupts another.